Efficient diffraction calculations using implicit convolution

Abstract

Diffraction calculations, such as Fresnel diffraction and the angular spectrum method, are essential in optical simulations. These methods are numerically calculated by discrete Fourier transform or fast Fourier transform (FFT). Although these diffraction calculations require FFT-based convolution, FFT-based convolution becomes circular convolution without using zero padding. Zero padding helps to avoid circular convolution, but increases calculation time and memory usage. This paper proposes efficient diffraction calculations using implicit convolution. The proposed diffraction scheme accelerates calculation time, reduces memory usage, and can be applied to any convolution-based diffraction.